Collection of Bathymetric and Wave Climate Data
The first step in the modeling process is the collection of information on the
seabed elevations over the computational area. This can be obtained from hydro-
graphic surveys of the area, digitizing nautical charts, or from digital topographic
databases such as those maintained by the National Oceanic and Atmospheric
Administration (NOAA).
Wave climate information close to the project site can be obtained from:
a. Long-term wave measurements at the project location.
b. Long-term wave measurements in deeper water with buoys such as those
operated by NOAA.
c. Hindcast from long-term wind observations using models such as Wave
Model (WAM), Wave Information Steady Wave Model (WISWAVE), or
Steady-State Wave Model (STWAVE).
Depending on the source of the wave climate data, simpler wave propagation
models such as STWAVE (Smith, Sherlock, and Resio 2001) or Refraction/
Diffraction Model for Spectral Wave Conditioning (REFDIF-S) (Kirby and
Ozkan 1994) might have to be run to transfer the wave climate data to the
boundary of the computational grid. Statistical techniques (e.g., Borgman 1972)
can then be used to reduce the wave climate data to design wave conditions with
associated return periods.
Information on tidal water levels and currents near the project site can be
obtained using prediction techniques based on long-term tidal observations (e.g.,
NOAA) or by running more sophisticated circulation models such as Advanced
Circulation (ADCIRC) Model for Oceanic, Coastal and Estuarine Waters. If the
current speeds exceed 10 percent of the phase velocity of the waves, the currents
could significantly modify the wave field and a 2-D circulation model would
have to be run to provide the spatial distribution of current speeds over the
computational area.
Preparation of Bathymetric Grid File
BOUSS-2D simulates wave propagation over a 2-D Cartesian grid as shown
in Figure 6. The computational domain is defined as a rectangular region from
(xorigin, yorigin) to (xmax, ymax) with uniform grid spacings ∆x and ∆y in the x and y
directions, respectively. The bathymetric grid represents the seabed elevation at
each node of the grid with land points defined as positive while water points are
defined as negative. To prepare the grid, the spatial extent and spacing of the
computational grid have to be selected. Factors to consider in the selection of the
grid boundaries and spacing include:
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Chapter 4 Setting Up and Running BOUSS-2D
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